Grass mowing machines for golf courses and other turf areas typically include one or more reel mower cutting units to provide an accurate, high quality cut. Each reel mower cutting unit includes a generally cylindrical reel that has a plurality of blades which rotate in close proximity to a stationary bedknife fixed with the frame of the cutting unit. Grass is cut by a shearing action between the bedknife and the rotating blades of the cutting reel.
Walk behind greensmowers typically include a ground engaging traction drum that propels the mower while mowing. The traction drum may be driven through a mechanical or hydraulic transmission connected to an internal combustion engine, electric motor, or other power source. The reel cutting unit may be driven by a hydraulic or electric motor.
Some walk behind greensmowers have reel cutting units that are driven by mechanical gears which in turn are driven by traction drive wheels at a fixed ratio such that the faster the ground speed, the faster the reel speed. For example, U.S. Pat. No. 8,261,523 for Clip Control System for Walk Reel Mower relates to a toothed timing belt entrained around three toothed pulleys that may be switched to different positions to change the clip rate.
Other walk behind greensmowers have reel mower cutting units that are driven by hydraulic motors, or cutting units driven by electric reel motors powered by batteries or an alternator driven by an internal combustion engine. Similarly, riding greensmowers and fairway mowers may include a vehicle with a traction drive system powered by an internal combustion engine, batteries or other power source. The vehicle may carry several reel mower cutting units, each powered by a hydraulic or electric reel motor.
Frequency of clip generally is measured by the distance the grass mowing machine travels forward before the next blade reaches the bedknife. Different climates, grasses and weather conditions require different clip frequency settings for ideal maintenance. In most cases, a single machine may be used to mow multiple areas on a golf course, but it can be difficult and time consuming to adjust the clip frequency.
To maintain a requested frequency of clip, the ground speed and the reel motor speed both may be constant. For example, U.S. Pat. No. 6,339,916 for Method for Constant Speed Control for Electric Greens Mower relates to an electric greensmower that includes a constant speed control mechanism.
Alternatively, a requested frequency of clip may be maintained by using a sensor to monitor the actual ground speed in a closed loop control system. The monitored ground speed may be provided as feedback to control the reel motor speed. For example, U.S. Pat. No. 5,394,678 for Electronic Control for Turf Maintenance Vehicle and U.S. Pat. No. 5,657,224 for Turf Maintenance Vehicle Diagnostics and Parameter Condition Logger relate to a controller that controls the speed of the reels by providing a pulse width modulated signal to valves of hydraulic reel motors. Ground speed is determined by measuring the rotation of a transmission gear driving the wheels, and a look-up table is used to determine a set point for reel speed. U.S. Pat. No. 5,497,604 for Supervisor Switch for Turf Mower has a controller that monitors ground speed of the mower, determines if the speed is approaching a maximum mowing speed, and actuates a warning to alert the operator if the maximum mowing speed is being approached or exceeded.
Similarly, U.S. Pat. No. 7,168,227 for Internal Combustion Engine Traction Drive With Electric Cutting Unit Drive For Walking Greens Mower relates to a controller for varying the rotational speed of an electric motor for the cutting reel based on output signals from a sensor coupled to at least one of the rollers, which the controller uses to determine the drive speed of the greens mower. U.S. Pat. Nos. 7,367,173 and 7,610,738 for Greens Mower Data Display and Controller relate to a vehicle controller that actively controls the electric reel motor based on a programmable vehicle clip rate data input and the monitored vehicle groundspeed. U.S. Pat. No. 7,954,308 for Frequency Of Clip Adjustment System And Method For Reel Mower Cutting Unit relates to a reel motor controller that provides a rotational speed to an electric reel motor based on the alternator voltage, voltage output from a user interface, an engine to traction roller ratio, a traction roller circumference and number of blades of the cutting reel. U.S. Pat. No. 8,621,833 for Lawn Mowing Vehicle With A Control Unit For The Motor controls the rotational speed of the electric reel using a speed detection unit detecting the travel speed of the vehicle and a control unit that controls the electric reel motor depending on the detected result of the speed detection unit.
Alternatively, the ground speed and reel motor speed each may be set by the operator independently and without specifying the frequency of clip. U.S. Pat. Nos. 6,487,837 and 6,802,175 for Articularly Mounted Battery-Powered Walk-Behind Reel Lawnmower relate to a greensmower having an electrical system with a variable resistor controlled by the operator to adjust the traction speed. Another resistor may be connected with the reel motor, and may be under the control of the operator and variable so the rotation speed of the reel may be adjusted. Similarly, U.S. Pat. Nos. 6,523,334, 6,758,030, 7,007,446 for Battery-Powered Walk-Behind Greensmower, and U.S. Pat. No. 7,434,642 for Battery Tray And Wiring Harness For A Walk-Behind Reel Greensmower, relate to an electric reel motor that is controlled by a fixed control or a potentiometer so that reel rotation speed may be variable and under the direct control of the operator.
A frequency of clip control system is needed for walk behind greensmowers and riding greensmowers or fairway mowers that does not require a closed loop control system with a sensor to monitor actual ground speed.